1. Technical Field
The present invention relates to image sensor modules, and more particularly, to a manufacturing method and structure for a wafer level image sensor module with fixed focal length contributing to reduced height and simplified process of wafer level image sensor modules.
2. Description of Related Art
In a conventional camera module, there are an image sensor, an IR filter, lenses and a holder for holding the above components. The image sensor is a semiconductor device for capturing images of articles and is widely used in digital still cameras (DSCs), digital video cameras (DVs), security monitoring systems, mobile phones, vehicle image sensor modules and other electronic products. For catering to the demands of various electronic products about compactness and mass manufacturing, it is desired to effectively simplify the manufacturing process and downsize image sensor modules, and therefore all the related manufacturers have worked hard to improve the manufacturing process and structure.
There are two major approaches to packaging image sensor modules. The first one is the so-called COB (Chip On Board) process, in which an image sensing chip is directly installed on a substrate and metal wires are provided to electrically connect the image sensor chip and the substrate. Then, a transparent lid (such as a glass window) is mounted above the image sensor chip to allow light to pass through the transparent lid and be captured by the image sensor chip. The other approach is known as the CSP (Chip Scale Package) process. Image sensor modules packaged through the chip level packaging method are more desired as the compactness of the packaged structures is considered.
However, problems and limitations occur when the COB process is implemented to package image sensor modules, including the low production rate due to the unit level packaging, high defective rate caused by dust introduced during the process, high cost for building and maintaining clean rooms, limitation to microminiaturization, and so on.
From the above description, it is learned that the production yield highly depends on the adopted packaging process and structure, and downsizing image sensor modules in height and volume is generally desired. Besides, significantly reducing the cycle time of the process for manufacturing image sensor modules and improving throughput as well as overall production yield of the products would also be helpful to expand application scope of image sensor modules on the market.